<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>获得字符串第 N 个位置的字符</title>
</head>
<body>
    
</body>
</html>
<script>
    var Arr = prompt('请输入字母，判断它在第几个位置')
    var arr = 'qwertyuiopasdfghjklzxcvbnm'
    for(var i=0;i<arr.length;i++){
        alert(arr.charAt(Arr))
        break;
    }
</script>